大きなストレスは辛いものだが、何とかそれをお解決しようという力を起こさせ、人が成長する気かっけになることも多いという。this sentence means big stress is distressful, but somehow without solving the problem, at the same time people will become more mature?or big stress is distressful but it will be solved as you grow up??

目的のためには手段を選ばない人だ。this means people will do anything to accomplish their goal..but i dont understand 手段を選ばない means you dont choose way?

As for the first sentence, the last part could be:何とかそれを「」解決しようという力を...人が成長する「きっかけ」になることも多いという。The latter part:It is said the stress leads you manage to solve the problemand this will often trigger to mature you.

devinamaaa wrote:目的のためには手段を選ばない人だ。this means people will do anything to accomplish their goal..but i dont understand 手段を選ばない means you dont choose way?

Yes. 手段を選ばない is a common idiom "to do anything (even if it's dirty or risky etc)".And it's used usually in a negative way.